Apolipoprotein B level and diabetic microvascular complications: is there a correlation?

Introduction

Dyslipidemia has long been implicated in diabetic complications. However, many subgroups have been considered to be responsible. Furthermore, a cause and effect relationship has long been debated. Apolipoprotein B (Apo B) is an exact measure of the total number of very low-density lipoprotein and low-density lipoprotein particles; thus, total plasma Apo B is a reliable surrogate for actual low-density lipoprotein particle number irrespective of its size. Hence, it is a better indicator of the correlation between dyslipidemia and diabetic microvascular complications.

Aim of the work

Our aim is to study the correlation between Apo B and diabetic microvascular complications, namely, nephropathy and retinopathy.

Materials and methods

A cross sectional study was carried out of 56 diabetic patients, 36 men and 20 women, both type 1 and 2, who were chosen randomly from the outpatient Endocrinology Clinic in Cairo University. Serum creatinine, estimated glomerular filtration rate, urine albumin/creatinine ratio (A/C ratio), and Apo B levels were determined. Groups were divided according to the A/C ratio as follows: no proteinuria (A/C ratioo30 mg/g), incipient proteinuria (30–300 mg/g), and overt proteinuria (4300 mg/g). We performed fundus examination as well as fluorescein angiography in patients with retinopathy. Patients on dialysis, HBA1c more than 7.5, on lipid-lowering treatment, or with familial hyperlipidemia were excluded. Calculations were carried out using the SPSS v.10 statistical software.

Results

We found a significant positive correlation between Apo B levels and microvascular complications. Apo B was higher with overt nephropathy than incipient nephropathy (1.75 ± 0.38), and higher in patients with incipient nephropathy (1.4 ± 0.48) than in patients without nephropathy (1.02 ± 0.34, Po0.01). A highly significant correlation was detected between the grades of retinopathy and the Apo B level. Finally, a significant positive correlation was detected between the presence of maculopathy and Apo B. Apo B levels were significantly higher in the presence of both nephropathy and retinopathy (1.26 ± 0.389) than in the absence of both complications (0.77 ± 0.361, Po0.05).

Conclusion

Apo B levels are strongly correlated to diabetic microvascular complications. The higher the degree of nephropathy, the higher the Apo B level. The presence of more than one microvascular complication correlates positively with high levels of Apo B. This suggests the possible use of Apo B as a sensitive biomarker of the presence of early diabetic microvascular complications.